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It was first suggested in the 18th century that symptoms arising from a head injury are not due to a fractured skull, but to injury of the brain. Percival Pott (1713-1788) was one of the first to emphasize that it was the neurological status and not the skull fracture that determined whether surgical intervention was indicated. One of the most notable instances of brain injury took place in the 1800s. Phineas Gage survived an accident where an iron rod penetrated his head and destroyed a good portion of his left frontal lobe. Prior to his accident, Gage was described as “even-tempered”, but his demeanor shifted significantly afterwards. Due to the definitive nature of his injury and the personality changes that followed, many cite this as the first case illustrating mood and personality shifts directly resulting from a brain injury.
The 20th century saw the advancement of technologies that improved treatment and diagnosis such as the development of imaging tools including CT and MRI, and, in the 21st century, diffusion tensor imaging (DTI). The introduction of intracranial pressure monitoring in the 1950s has been credited with beginning the "modern era" of head injury.<ref name="Arti12">Marshall, L. F. (2000). Head Injury: Recent Past, Present, and Future. Neurosurgery, 47(3), 546–561. https://doi.org/10.1097/00006123-200009000-00002</ref> In the 1970s, awareness of TBI as a public health problem grew, and a great deal of progress has been made since then in brain trauma research, such as the discovery of primary and secondary brain injury. Prevention of TBI has also become immensely important with several efforts made in that direction such as: introduction of helmets in the army and motorcyclists, airbags in motor vehicles etc. The 1990s saw the development and dissemination of standardized guidelines for the treatment of TBI, with protocols for a range of issues such as drugs and management of intracranial pressure.
== Mechanism of Traumatic Brain Injury ==
The mechanical force applied to the head displaces the brain. Depending on the direction and magnitude of the force, certain neurological functions can be disrupted. The damage to the brain within the skull can present as strain, tissue distortion and shearing of axons. The processes for damage control are activated immediately, while the damage continues to evolve. The damage occurs as a result of the cellular and molecular processes taking place in response to mechanical forces. First, the mechanical force disrupts the neuronal membrane, which rapidly increases the extracellular potassium concentration. This activates a positive feedback loop where more potassium ions are released, which leads to a cascade of responses that eventually lead to a period of hyperglycolysis in the brain followed by higher permeability of the Blood-Brain-Barrier (BBB) and the induction of cytotoxic edema in the brain.<ref name="Arti13">Giordano, K. R., & Lifshitz, J. (2021). Pathophysiology of Traumatic Brain Injury. In S. Honeybul & A. G. Kolias (Eds.), Traumatic Brain Injury. Springer. https://doi.org/10.1007/978-3-030-78075-3_2 </ref> The latter has a detrimental effect on all cells in the brain tissue.
Very important cell types in the brain, aside from neurons, are the neuroglia. These cell types are broadly recognized as having a supportive role. There are 6 types of neuroglia, each with their own function [see figure 1]. In the central nervous system (CNS), the astrocytes are a main type of glial cells. They contribute to the maintenance of homeostasis in the CNS through reactive astrogliosis.<ref name="Arti14">Sofroniew, M. V., & Vinters, H. V. (2009). Astrocytes: biology and pathology. Acta Neuropathologica, 119(1), 7–35. https://doi.org/10.1007/s00401-009-0619-8 </ref> This process is triggered by all types of brain insults and has features that aid recovery, but simultaneously have a potential to inflict damage on the brain. For example, the astrocytes break down their glycogen to supply adjacent neurons with lactate, which the neurons use as fuel to recover. However, the astrocytes also play a critical role in water movements through the brain and in pathological conditions, this can mediate oedema. In all cases of reactive astrogliosis, GFAP is up-regulated. The degree to which the GFAP expression changes, is only dependent on the severity of the trauma to the CNS and not on the morphological appearance of the reactive astrogliosis. <ref name="Arti15">Verkhratsky, A., & Butt, A. (2013). General Pathophysiology of Neuroglia. In Glial Physiology and Pathophysiology (1st ed.). John Wiley & Sons, Ltd. https://doi.org/10.1002/9781118402061 </ref>
== References ==
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